Soil exhaustion is mostly irrelevant to this industrial method... it just means adding a more complete nutrient mix. In much of the US or Europe they can get a

Soil exhaustion is mostly irrelevant to this industrial method... it just means adding a more complete nutrient mix. In much of the US or Europe they can get awawy with only adding NPK (until, as you say, the soil gets exhausted, meaning some of the other nutrients are no longer available in sufficient quantity), but in a lot of the tropics (where I've practiced agriculture) the soils are so poor that they go with a complete nutrient mix from the start, i.e. treat the soil as just a substrate to hold the roots and add everything else, both macro and micro nutrients (often in the irrigation water, so it's basically hydroponics in soil). The method remains the same.